Nunung, Fidiatur RRifardiEdwar, Rufli2014-11-092014-11-092014-11-09Dodyhttp://repository.unri.ac.id/xmlui/handle/123456789/6520The research was conducted in March to April 2011 in Dumai coastal waters. The purpose of this research was to understand the materials composing the sediment profiles vertically. Field survey method was applied with location of study consisting 7 stations. Sediment samples were taken by using the Gravity core, in every station a length of 12 cm was cut and divided into 5 layers with thickness of 1 cm. Sediment sample obtained from field was analyzed in laboratory by using sand composition analysis. The result showed that sediment composition found consisting of lithogenous sediment (rock fragment, mica and quartz) and biogenous (plant fibers, foraminifera and mollusc). The vertical composition difference was not clear. Rock fragment dominated at every layer in stations north and west sides of PT. Pertamina UP II Dumai indicate rock fragment supply proceed from erosion of land and abrasion caused by tidal current and wave. In stations of east sides from PT. Pertamina UP II Dumai the upper and lower layers dominated by plant fibers that could be coming from mangrove decomposition in this area. The overall results indicate that all sediment materials in the area were derived from the similar source, thus reflecting the small differences in the sediment material. Keyword : composition, vertical sediment, Dumai coastCompositionVerticalDumaiUR-Scientific Work Lecturer